Communication apparatus, communication method, and communication system

ABSTRACT

A communication apparatus includes a frame generating device configured to generate a physical frame containing, of a plurality of MAC frames to be transmitted, a MAC frame which requires acknowledgement indicating that the frame is received by a receiving side, a MAC frame which does not require the acknowledgement, and identification information which indicates necessity/unnecessity of acknowledgement for each MAC frame depending on whether each MAC frame requires acknowledgement, and a transmitting device configured to transmit the physical frame generated by the frame generating device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromprior Japanese Patent Application No. 2004-063237, filed Mar. 5, 2004,the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates a communication apparatus, communicationmethod, and communication system which perform media access control and,more particularly, to access control for improving quality of service(QoS).

2. Description of the Related Art

Media access control (MAC) is control for causing a plurality ofcommunication apparatuses which perform communication while sharing thesame medium to decide how to use the medium in transmittingcommunication data or management frame. Owing to media access control,even if two or more communication apparatuses transmit communicationdata (or management frame) by using the same medium at the same time,there is less chance of the occurrence of a phenomenon (collision) inwhich a communication apparatus on the receiving side cannot decodecommunication data. The fundamental access method of the IEEE802.11 MACis CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance). TheCSMA/CA is designed to reduce the collision probability. Media accesscontrol is also a technique for controlling access from communicationapparatuses to a medium so as to minimize the chance of the occurrenceof a phenomenon in which, despite the presence of communicationapparatuses having transmission requests, the medium is not used by anyof the communication apparatuses.

In addition, several access control techniques designed to improvequality of service (QoS) are also known. For example, there is availableHCCA (HCF Controlled Access) which is an extended technique of aconventional polling sequence and is used as a QoS technique ofguaranteeing parameters such as a designated bandwidth and delay time.According to HCCA, in order to guarantee parameters such as bandwidthand delay time, QAP (QoS Access Point) performs bandwidth managementincluding allocation of transmission opportunity to QSTA (QoS Station).QAP is also known as HC (Hybrid Coordinator) in IEEE802.11e standard.

Jpn. Pat. Appln. KOKAI Publication No. 2002-314546 discloses a method ofassigning priorities to communications between wireless networkstations, while referring to QoS in the IEEE 802.11e standard.

According to conventional HCCA, quality can be guaranteed for eachtraffic stream, and data transmission corresponding to priority can berealized. A Traffic Stream is a set of MSDU (MAC Service Data Unit) s tobe delivered subject to the QoS parameter values provided to the MAC ina particular traffic specification. Traffic Streams are only meaningfulto MAC entities that support QoS within the MAC data service. Such QoSis also preferably used in a new communication scheme in which a furtherincrease in throughput is achieved. For example, QoS is preferably usedfor frame aggregation designed to improve the transmission efficiency bytransmitting a plurality of MAC frames upon containing them in one PHY(physical) frame. If, however, a conventional frame aggregationtechnique is simply applied to QoS like HCCA, the following problemsarise.

According to the conventional frame aggregation technique, since noconsideration is given to the priorities of frames, when a series offrames in a transmission queue (TxQ) are aggregation target frames, anFTP (File Transfer Protocol) frame with a relatively low priority may beextracted before a VoIP (Voice over IP) frame with a high priority andaggregated to a transmission aggregation frame. This may hinder theassurance of QoS in consideration of the priorities of frames.

In addition, the frame aggregation technique using a selective repeatretransmission needs to be in combination with an acknowledgementsequence (e.g., a “No acknowledgement”) unique to IEEE802.11e standard.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to provide a communication apparatus,communication method, and communication system which can increasethroughput by aggregating multiple (a plurality of) MAC frames whilemaintaining the service quality (QoS) of communication.

A communication apparatus according to an aspect of the presentinvention includes a frame generating device configured to generate aphysical frame containing, of a plurality of MAC frames to betransmitted, a MAC frame which requires the reception status ofacknowledgement frame from a receiving side, a MAC frame which does notrequire the acknowledgement, and identification information whichindicates necessity/unnecessity of acknowledgement for each MAC frame,and a transmitting device configured to transmit the physical framegenerated by the frame generating device.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a block diagram showing the arrangement of a communicationapparatus according to an embodiment of the present invention;

FIG. 2 is a view showing an example of a frame format used by thecommunication apparatus according to an embodiment of the presentinvention;

FIG. 3 is a view for explaining frame aggregation without considerationto priority;

FIG. 4 is a view showing the types of QoS in the IEEE 802.11e standard;

FIG. 5 is a view for explaining HCCA in the IEEE 802.11e standard;

FIG. 6 is a view showing the format of each MAC frame to be aggregated;

FIG. 7 is a view showing a TS setup sequence;

FIG. 8 is a view showing the format of a TSPEC;

FIG. 9 is a view showing the contents of an Ack policy field;

FIG. 10 is a view showing an example of how TSs and TSPECs are set;

FIG. 11 is a view showing STA queues and priority subqueues;

FIG. 12 is a view showing an extended bitmap of an Ack policy bitmap;

FIG. 13 is a view for explaining a retransmission control example (A);

FIG. 14 is another view for explaining the retransmission controlexample (A);

FIG. 15 is a view for explaining a retransmission control example (B);

FIG. 16 is another view for explaining the retransmission controlexample (B);

FIG. 17 is a view showing frame aggregate examples 1 and 2 for eachpriority;

FIG. 18 is a view for explaining frame aggregation for each priority;

FIG. 19 is a view showing the format of a TCLAS element;

FIG. 20 is another view showing the format of a TCLAS element;

FIGS. 21A and 21B are views respectively showing ADDTS Request (request)and ADDTS Response (response);

FIG. 22 is a graph showing the relationship between the channelestimation accuracy and the temporal position of frame aggregation onthe format;

FIG. 23 is a view for explaining an example of sliding window control inretransmission for each priority;

FIG. 24 is another view for explaining an example of sliding windowcontrol in retransmission for each priority;

FIG. 25 is still another view for explaining an example of slidingwindow control in retransmission for each priority;

FIG. 26 is a view showing an example of a Block Ack sequence;

FIG. 27 is a view showing a format in a case wherein block Ack requestsfor the respective TSs are aggregated into one PHY frame;

FIG. 28 is a view showing a format in a case wherein Block Ackinformation for the respective TSs are aggregated into one PHY frame;

FIG. 29 is a view showing an example of a immediate Block Ack framesequence; and

FIG. 30 is a view showing an example of a delayed Block Ack framesequence.

DETAILED DESCRIPTION OF THE INVENTION

The embodiments of the present invention will be described withreference to the views of the accompanying drawing.

FIG. 1 is a block diagram showing a communication apparatus according toan embodiment of the present invention. A communication apparatus 100 isan apparatus configured to communicate with another communicationapparatus through a wireless link, and includes processing units 101,102, and 103 respectively corresponding to a physical layer, MAC layer,and link layer. These processing units are implemented as analog ordigital electronic circuits or as firmware or the like to be executed bya CPU incorporated in an LSI in accordance with implementationrequirements. An antenna 104 is connected to the physical layerprocessing unit (“processing unit” will be omitted hereinafter) 101. TheMAC layer 102 includes an aggregation processing device 105 according tothe present invention. The aggregation processing device 105 includes acarrier sense control device 106 and retransmission control device 107.

FIG. 2 is a view showing an example of the frame format used by thecommunication apparatus according to an embodiment of the presentinvention. A frame format 200 schematically shows a frame structureassociated with a physical layer and MAC layer. More specifically, thisformat is assumed to be one that conforms to IEEE 802.11 or an extendedversion thereof. As shown in FIG. 2, the frame format 200 is comprisedof a PHY header 201, MAC super frame header 202, MAC super frame payload203, and PHY trailer 204. The MAC super frame header 202 and MAC superframe payload 203 correspond to a PHY payload (to be described later).The PHY header 201 is processed by the physical layer 101 of thereceiving communication apparatus. That is, the physical layer 101performs detection of a frame head, carrier sense, timingsynchronization establishment, automatic gain control (AGC) of anamplifier, tracking a transmitting-side carrier frequency (automaticfrequency control), transmission channel estimation, and the like. Thephysical layer 101 also detects the modulation scheme and coding ratioof the PHY payload following the PHY header 201, a transmission rate,and a data length.

In this description, a communication scheme for improving the transferefficiency by containing multiple (a plurality of) MAC frames in oneframe format 200 as shown in FIG. 2 will be referred to as “frameaggregation”. Frame aggregation is suitable for the next-generationhigh-throughput wireless LAN communication (IEEE 802.11n standard) whichis currently being standardized.

The first to third embodiments of the present invention which will bedescribed below are directed to QoS when frame aggregation is executed.QoS to be described in each embodiment is assumed to be HCCA whichguarantees given quality for each traffic stream.

The first embodiment will exemplify frame retransmission controlassociated with communication quality and communication sequences forvarious kinds of response policy (Ack Policy).

Conventionally, in the frame aggregation scheme, no priority processingis performed for each flow (application traffic) directed to eachdestination. When, for example, as shown in FIG. 3, a series of frames301 in a transmission queue (TxQ) 300 are aggregation target frames, anFTP (File Transfer Protocol) frame with a relatively low priority issometimes aggregated preferentially over a VoIP (Voice over IP) framewith a high priority. In the second embodiment, in order to prevent anyframes with low priorities from being transmitted before frames withhigh priorities due to the execution of simple frame aggregation method,frame positions at which frames to be aggregated are stored are sortedaccording to priority. The third embodiment will exemplify a casewherein when a frame having undergone a reception error is to beretransmitted, suitable sliding window control is executed in QoS basedon the HCCA scheme. The fourth embodiment is directed to the aggregationof Block Ack frames (control frames which are defined in IEEE802.11estandard) associated with QoS.

FIG. 4 is a view showing the types of QoS in the IEEE 802.11e standard.QoS in the IEEE 802.11e standard includes DCF (Distributed CoordinationFunction) 400, PCF (Point Coordination Function) 401, EDCA (EnhancedDistributed Channel Access) 402, and HCCA (HCF Controlled ChannelAccess) 403. In the DCF 400, a transmitting STA senses a wireless mediumto determine whether any other STA is transmitting, thereby deciding, inaccordance with the state of use of the wireless medium, whether or notto transmit a frame. In this case, a carrier sense time is the sum of anIFS (Inter Frame Space) time and a random backoff time. In the PCF 401,an AP (Access Point) serves as a base station which performs polling forcentralized control on wireless terminals. The AP sequentially pollsterminals on the basis of a polling list. An STA transmits a frame afterit receives a poll frame. The prioritized EDCA 402 is a contention-baseQoS scheme, in which multiple (a plurality of) ACs (Access Categories)are provided for the respective priorities to perform CSMA/CA procedurein parallel. The HCCA 403 is an extended scheme of conventional PCF forpolling control.

FIG. 5 is a view for explaining HCCA in the IEEE 802.11e standard. InHCCA, a QoS access point (QoS-AP) 109 called HC (Hybrid Coordinator) isa polling (scheduling) entity.

When communication is to be started, a TS (Traffic Stream) is set up(Uplink, Downlink, Bidirectional) between the QoS-nonAP-STA (QoSterminal other than an access point; to be referred to as “QSTA”hereinafter) 100 and the HC 109. The setup of the TS is started by aQSTA serving as an entity. The TS is a path for data frames whichindicates what type of traffic (e.g. VoIP or FTP) the terminal uses andwhat amount of bandwidth is required. The specification of the TS isuniquely determined by a TSPEC (Traffic Specification). The TSPEC storesinformation such as the maximum allowable delay interval (MaximumService Interval) of a flow and a TSID (Traffic Stream ID) foridentifying a traffic stream. In this case, the most important parameteris a mean data rate that defines average data rate specified at MAC-SAP.

The TSPEC notified as a parameter for QoS control notified from the QSTA100 to the HC 109 is used for scheduling utilized by the HC 109. Notethat multiple (a plurality of) TSs can be set for each application to beused. The HC 109 then executes a polling sequence for the QSTA 100 inaccordance with the TS. A practical algorithm for scheduling in thepolling sequence is not defined in IEEE 802.11e, and hence isimplementation-dependent. When a TXOP (Transmission Opportunity;allocated transmission time) is given to the QSTA 100 by polling fromthe HC 109, the QSTA 100 can transmit multiple frames in the allowedperiod of time.

According to the HCCA scheme, since each MAC frame has its own TIDs(Traffic ID) in communication with a QSTA, a plurality of trafficstreams can be aggregated.

FIG. 6 is a view showing the format of each MAC frame in the IEEE802.11estandard. When frame aggregation method is to be executed with HCCAprotocol, each MAC frame 600 has a unique MAC header 601 and canuniquely specify a TS by the TID in the MAC header 601. No criticalproblem therefore arises in terms of compatibility between HCCA andframe aggregation. A TID is written in a QoS control field (QoS control)602 extended for IEEE 802.11e to identify a traffic. The TID field'slength (0th to 3rd bits) is four bits. Of these ordinal numbers, TSIDsuse the eighth to the 15th.

The first to fourth embodiments will be described in detail below.

First Embodiment

The first embodiment of the present invention is directed to frameretransmission control associated with communication quality andcommunication sequences for various kinds of acknowledgement framesindispensable to retransmission procedure. More specifically, acommunication apparatus according to the first embodiment is designed totransfer an Ack policy for “No acknowledgement” defined in IEEE 802.11eand an Ack policy for partial Acks for frame aggregation. As describedabove, as QoS protocol, HCCA is assumed, which guarantees quality foreach traffic stream.

FIG. 7 is a view showing a TS setup sequence. A QSTA (communicationapparatus) 100 transmits a TSPEC embedded in an ADDTS Request message toan HC 109 at the start of each traffic transfer. IEEE 802.11e does notdefine which kind of parameter is to be selected. That is, a TSPEC isimplementation-dependent. When the ADDTS Request message is accepted bythe HC (SME (Station Management Entity) of the HC to be precise) 109, anADDTS Response is returned from the HC 109, thereby setting TS in dueform. Subsequently, the HC 109 performs scheduling such as sending dataor poll on the basis of the set TSPEC information of the TS.

FIG. 8 is a view showing the format of a TSPEC. When a TS is to be set,bandwidth at MAC-SAP required for the QoS flow is set in the mean datarate field of a TSPEC 800.

A TS Info field 801 of the TSPEC 800 includes an Ack policy field 802which indicates in what kind of acknowledgement scheme an MPDU (MACProtocol Data Unit) belonging to the corresponding TID should betransmitted.

FIG. 9 is a view showing the contents of an Ack policy field. Accordingto the first embodiment of the present invention, a value 902 equivalentto Reserved in the prior art is set as a partial acknowledgement(Partial_ACK) for frame aggregation. The MAC layer of a terminal whichtransmits a MAC super frame determines an Ack policy for each data framedescending from an upper layer. In this case, designating an Ack policyto a partial ACK means that “the data frame is set as a frameaggregation target, and an ACK response from the receiving side isrequired”. With regard to a TS in which “Partial_ACK” (902 in FIG. 9)and “No_ACK” (901 in FIG. 9) are designated in the Ack policy field 802of TSInfo in FIG. 8, the transfer of frame aggregation by a MAC superframe is supported (a plurality of TSs are added with different ADDTSs).

Conventionally, the Ack policy field 802 of TSInfo indicates what ACKmechanism is to be used to transfer a frame. As such mechanisms, threetypes of mechanisms, namely “Normal_Ack (Normal IEEE802.11acknowledgement)”, “No_ACK (No acknowledgement)”, and “Block_ACK (BlockAcknowledgement)”, have already been defined in IEEE 802.11e.

“Normal_Ack” is a normal data transmission method supported by IEEE802.11, in which after one unicast data is transmitted, the transmittingterminal (originator) waits for a predetermined period of time until itreceives an ACK frame from the destination terminal. When a timeoutoccurs, backoff procedure is performed again to retransmit the dataframe. The data frame designated in “Normal_Ack” is not set as a frameaggregation target, and is transmitted in accordance with a procedure inthe existing IEEE 802.11 standard.

“No_ACK” is a data transmission method used when a transmission channelis relatively stable. According to this method, a terminal transmits anew unicast data frame without waiting for the reception of an ACK framefrom a destination terminal.

“Block_ACK” is a data transmission method of consecutively transmittingunicast data frames at SIFS (Short Inter Frame Space) intervals. Thismethod is designed to realize selective repeat retransmission by usingBlock Ack frames. A plurality of acknowledgements belonging to the sameTID are combined into one Block Ack frame. That is, a plurality of BlockAck frames are required for each TS. In this method, a data frame withBlock Ack Policy is not set as a frame aggregation target, and a BlockAck transmission sequence in the existing IEEE 802.11e standard isexecuted.

FIG. 10 is a view showing an example of how TSs and TSPECs are set. Aplurality of TSs having independent Ack Policies are set for each TID. Aplurality of TSs with different TSPECs are set like Partial_ACK for FTP,No_ACK for Video, and Block_ACK for VoIP.

FIG. 11 is a view showing examples of STA queues and priority subqueues.In a communication scheme according to the first embodiment, HC preparestransmission queues (destination queues) 1100 and 1101 for eachdestination QSTA for which a TS is set. Subqueues 1102, 1103, and 1104are prepared in the destination queues 1100 and 1101. Note, however,that these subqueues are generated only for data frames in which the AckPolicies for TSPECs are designated to “No_ACK” and “Partial_ACK”. A QSTAalso generates a queue for each destination terminal and a subqueue foreach priority in the same manner as described above. Frames which arenot set in subqueues for the respective priorities in a destinationqueue (data frames of “Normal_ACK” and “Block_Ack” and managementframes) are stored in a normal transmission queue (TxQ, a beacon queue(BcQ) for beacons, or the like).

In the first embodiment of the present invention, when data transmissionis to be performed by frame aggregation, the data frames of both the AckPolicies of “No_ACK” and “Partial_ACK” can be packed into one PHY frame.This also means that all the data frames can be transmitted according tothe “No_ACK” policy and can also be transmitted according to the“Partial_ACK” policy. As described above, the “Partial_ACK” policy meansan Ack Policy that is applied to MAC frames which are frame aggregationtargets and require acknowledgement responses.

FIG. 12 is a view showing how an Ack Policy bitmap is extended. In thiscase, the maximum number of frames aggregated is set to eight. Thismaximum number is, however, implementation-dependent. In frameaggregation, a MAC super frame header 1200 is added to the head of a MACsuper frame. This header contains a header CRC (16 bits) 1201 and afield indicating the length (12 bits) of each of the aggregated MPDUs.

In this embodiment, as shown in FIG. 12, a new Ack Policy Bitmap field1202 is added. This bitmap indicates whether or not each MPDU aggregatedin the MAC super frame requires ACK (Partial_ACK in this case). If, forexample, the MPDUs in the MAC super frame are set like “ACK notrequired—ACK not required—ACK not required—ACK not required—ACKrequired—ACK required—ACK required—ACK required”, Ack Policy Bitmap isexpressed by “00001111” (the latter four bits are portions requiring apartial Ack bitmap).

A terminal which has transmitted a MAC super frame basically caches AckPolicy Bitmap information. A copy of a transmitted data frame isbuffered to prepare for retransmission until a Partial Ack frame isreceived. Since a data frame for which “ACK not required” is designatedis not retransmitted upon the timeout of an acknowledgement, there is noneed to store a copy of the frame after transmission. In contrast, withregard to a data frame for which “ACK required” is designated, the framemust be buffered to prepare for retransmission. If, however, frames forwhich “ACK not required” (No_ACK) are not stored, the transmitting sidepreferably caches relative positional information of a transmitted dataframe corresponding to “ACK required”, whose copy is stored on thetransmitting side and a data frame corresponding to “ACK not required”(no copy thereof is stored) (an implementation method having no relativepositional information will be described later).

Upon receiving a MAC super frame, the terminal determines whether thissuper frame is addressed to itself, and performs CRC (Cyclic RedundancyCheck) calculation for each MPDU. Thereafter, the terminal checks theAck Policy Bitmap field 1202 in the MAC super frame header. If a flag of“1” indicating the necessity of an acknowledgement is set, the value “1”or “0” is set in the corresponding bitmap of the Partial Ack frame (ifit is determined upon CRC calculation that the frame has been properlyreceived, “1” is set; otherwise, “0” is set). An MPDU in which the AckPolicy Bitmap is “0” desires transfer by “No_ACK”. In this case,therefore, the value “0” is set regardless of the CRC calculationresult.

If no Partial Ack frame can be received from the destination terminaleven after the lapse of a predetermined period of time since thetransmission of a MAC super frame, data frames for which the“Partial_ACK” policy has been designated and which have been bufferedcan be aggregated into a MAC super frame, and new data framescorresponding to “No_ACK” policy can be aggregated. In this case, theretransmission of a data frame is abandoned after the lapse of apredetermined period of delay bound of the TSPEC.

When the terminal which has transmitted the MAC super frame receives aPartial Ack from the destination terminal, the transmitting terminalchecks the Partial Ack Bitmap using the Ack Policy Bitmap informationcached in it. If the bit information of the Partial Ack Bitmap is “0”,the corresponding data frame is retransmitted.

Since a TS is used in the channel access scheme based on HCCA, eachterminal can transmit/receive a MAC super frame and Partial Ack frame atSIFS intervals for the period determined by TXOP. If all the framesaggregated into the MAC super frame are those designated with “No_ACK”(i.e., all the Ack Policy Bitmap fields are 0), a new MAC super frame isgenerated and transmitted after the lapse of SIFS without waiting for aPartial Ack.

The coexistence of the “No_ACK” policy and “Partial_ACK” policy will bedescribed in detail below with reference to two retransmission controlexamples.

In a retransmission control example (A), the transmitting side cachesthe relative positional information of Ack Policies in advance. As shownin FIG. 13, when transmitting a MAC super frame 300, the transmittingterminal 100 caches in advance bitmap information 3002 indicatingrelative positions which indicate which MPDUs of the aggregated MPDUsrequire acknowledgements (“Partial_ACK” must be dealt with on thereceiving side) and do not required ACKs (No_ACK policy). As indicatedin an Ack Policy Bitmap 3001, the first half frames with sequence number“1” to “4” in the MAC super frame 300 correspond to “No_ACK”, i.e.,TSIDs which do not require ACKs, whereas the second half frames “1” to“4” correspond to Partial_ACK, i.e., TSIDs which require ACKs.

A receiving terminal (recipient) 110 refers to the Ack policy bitmap inthe MAC super frame header of a received frame 400. The receivingterminal 110 performs CRC calculation, and if it is determined that theframe is properly received and the frame needs acknowledgement, thecorresponding information is written in a Partial Ack 401, and isreturned to the transmitting side (in the example shown in FIG. 14, “1”is set in a Partial Ack Bitmap 4010).

Assume that the transmitting terminal 100 determines, on the basis ofthe Partial Ack Bitmap 4010 and the Ack policy relative positionalinformation 3002, that MPDUs whose Ack policies are not “No_ACK” (i.e.,portions requiring ACKs) have not been properly transmitted. In thiscase, the corresponding MPDUs are aggregated as retransmission targetsinto a MAC super frame 301 again and retransmitted. Since there is noneed to retransmit portions whose Ack Policies correspond to “No_ACK”,they may be released from a retransmission buffer (if copies of “No_ACK”policy frames have been buffered), and new frames may be packed in theMAC super frame. In the example shown in FIG. 14, when MPDUs “1” and “2”which require ACKs from the receiving side are to be packed in the MACsuper frame 301, MPDUs “5” to “8” which are new sequence numbers whichcorrespond to the No_ACK policy are simultaneously aggregated.

A characteristic feature of the above retransmission control example (A)is that information sent to the transmitting side in the form of aPartial Ack Bitmap is equivalent to “a bitmap for indicating properlyreceived MPDUs”.

In a retransmission control example (B), the transmitting terminaldetermines MPDUs to be retransmitted on the basis of a Partial AckBitmap from the receiving side. In the retransmission control example(A), the transmitting side caches in advance the relative positionalinformation 3002 of portions corresponding to the No_ACK policy andportions requiring Partial Acks. In contrast to this, in theretransmission control example (B), the meaning of the bitmap in aPartial Ack is changed, and the transmitting terminal requests “a bitmapfor MPDUs to be retransmitted” instead of “a bitmap corresponding toproperly received MPDUs” from the receiving side (so-called NACK). Inthe retransmission control example (B), the transmitting terminal 100need not cache any special information as long as it buffers the MPDUsfor retransmission.

As shown in FIG. 15, upon receiving a MAC super frame 400, the terminal110 refers to an Ack policy bitmap 3001 in the MAC super frame header torecognize MPDUs which require ACKs, as in the retransmission controlexample (A). If a bit of the Ack Policy Bitmap 3001 is set, and the CRCcalculation result on the corresponding MPDU indicates an error, a bitrepresenting a retransmission request is set, and a partial Ack 402 isreturned to the transmitting terminal 100.

As shown in FIG. 16, the transmitting terminal 100 refers to a PartialAck Bitmap 4020 in the Partial Ack 402 from the receiving terminal 110.If a bit corresponding to a portion to be retransmitted is set (“1” inthe case shown in FIG. 16), the transmitting terminal 100 determinesthat the corresponding MPDU should be retransmitted. The subsequentprocessing is the same as in the retransmission control example (A).

As described above, according to the first embodiment of the presentinvention, adding an extended field to a MAC super frame header makes itpossible to realize a communication apparatus which can use both Ackpolicies of “No_ACK” and “Partial_ACK” in combination with each other.The first embodiment can also be adaptable for negativelogic.

Second Embodiment

The second embodiment of the present invention is directed to acommunication apparatus which, when transmitting MAC frames withdifferent priorities, performs frame aggregation upon dividing the MACsuper frame payload in the MAC super frame according to the priorities.

Assume that unicast data frames with different priorities are aggregatedby using conventional frame aggregation without any change. In thiscase, there is a chance that the frames are randomly packed in the MACsuper frame like “low”, “high”, “intermediate”, “high”, “low”, “high”,“intermediate”, and “intermediate”. According to the characteristics ofa wireless propagation path, as the PHY frame length increases, errorstend to occur more easily toward the end of the frame, resulting in adeterioration in transmission efficiency.

According to the second embodiment of the present invention, therefore,frame aggregation is executed after the payload is divided according tothe priorities of the frames like “high”, “high”, “high”,“intermediate”, “intermediate”, “intermediate”, “low”, and “low”.

If, for example, frames corresponding to a traffic stream using the“No_ACK” policy are arranged in the front part, and frames correspondingto a traffic stream with a relatively low priority are arranged in therear part, efficient transfer can be realized. This is because theretransmission of a frame with a low priority due to a reception erroris more allowable than the retransmission of a frame with a highpriority.

FIG. 17 is a view showing frame aggregate examples 1 and 2 formed on apriority basis. The method of aggregating frames upon dividing thepayload according to the priorities can be implemented more easily byusing a priority subqueue for each STA. The number of MPDUs for eachpriority is determined in accordance with, for example, Mean Data Rateindicated by a TSPEC. If there are no MPDUs which have differentpriorities, as many MPDUs corresponding to the TS as possible arepacked, as in aggregate example 2.

For example, as shown in FIG. 18, frames are extracted from a main queue(TxQ) 210 for respective STAs and respectively stored in prioritysubqueues 2100 to 2103 for the respective STAs (STA 1 to STA 4 in thiscase). First of all, with regard to the subqueue 2100 for the STA 1,four frames are extracted from the VoIP subqueue. Three frames are thenextracted from the Video subqueue and arranged after the VoIP framegroup. One frame is further extracted from an FTP subqueue and placedafter the Video frame group, thereby constructing a MAC super frame 211.With regard to the subqueue 2101 for the STA 2, four frames areextracted from the Video subqueue. Two frames are then extracted fromthe FTP subqueue and arranged after the Video frame group, therebyconstructing one MAC super frame 212. With regard to the subqueue 2102for the STA 3, since all the subqueues are empty, no transmission isperformed. With regard to the subqueue 2103 for the STA 4, five framesare extracted from the FTP subqueue to construct one MAC super frame213. The number of frames extracted from each priority subqueue isimplementationdependent.

The definition of priority will be described in detail below.

(1) TCLAS (Traffic Classification)

A TCLAS specifies certain parameter values to identify the MSDUsbelonging to a particular traffic stream. The classification processperformed above MAC-SAP at a HC uses the parameter values for given TSto examine each incoming MSDU and determine whether this MSDU belongs tothat TS. FIGS. 19 to 20D are views showing the format of a TCLASelement. Classifier (classification process) on MAC-SAP distributesMSDUs from an upper layer for each TS set up by itself. If, for example,IPv4 exists as an upper layer protocol as shown in FIG. 20B, theClassifier process determines a specific TS for mapping by using an IPaddress, port number, and DSCP (Diffserve Code Point: the identificationinformation of an IP packet used for QoS service Diffserve(Differentiated Services) implemented on the IP layer).

(2) TSPEC (Traffic Specification)

The QoS characteristics of a data flow to and from a non-AP-QoSSTA. Themain purpose of a TSPEC is to ensure a resource in an HC and change thebehavior of scheduling of the HC. A TSPEC also defines the Ack Policy ofa data frame (identified by a TSID) flowing through the TS. A TSPEC isgenerated by an SME (Station Management Entity) in a MAC in accordancewith a request from an application.

A TS has one or more TCLASs (depending on the determination by a QSTAwhich sets the TS). TCLASs are mapped in the TS. The HC is notified ofthe information of a TSPEC and TCLAS by ADDTS procedure from the QSTA.FIG. 21A shows the contents of an ADDTS Request. FIG. 21B shows thecontents of an ADDTS Response.

When the negotiation of a TS is properly performed, the TS isdiscriminated in the QSTA on the basis of the TSID and direction(Uplink, Downlink, Bi-directional) information, and is discriminated inHC on the basis of the TSID, direction information, and the addressinformation of the QSTA.

Note that even if the direction of the TS is Downlink from an HC to aQSTA, the QSTA becomes an initiator for TS setup.

In summary, when given application data (e.g., VoIP) is sent from anupper layer to a MAC layer, the application data is mapped in the TSassociated therewith in accordance with the information (IP address,port number, DSCP, and the like) of a TCLAS. Each data frame has TIDidentification information (the TSID of VoIP in this case) in the MACheader, which is used for data/poll transmission scheduling. Note thatin HCCA, no frames other than those corresponding to the set TS aretransmitted. In order to transmit such frames, a new TS must be set.

In OFDM, channel estimation (estimating phase and amplitude distortionsin a transmission channel for each subcarrier) is performed by using aknown preamble signal (long symbol in IEEE 802.11a) stored in areceiving terminal. A wireless LAN which performs communication in thepacket mode and in which time variations in transmission channel in eachpacket (frame) are small generally uses a technique of independentlyperforming channel estimation at the head of a preamble signal for eachpacket.

If, however, the frame length increases like a MAC super frame, since atransmission channel varies with time, the estimation result calculatedat the time of the reception of a preamble may not accurately bereflected in the second half part of the frame with higher possibility.Packing MPDUs with high priorities in the first half part of a MAC superframe as in the second embodiment makes it possible to improve the errortolerance of high-priority data.

FIG. 22 is a graph showing the relationship between the channelestimation accuracy and the temporal position of frame aggregation onthe format. The ordinate represents the channel estimation accuracy; andthe abscissa, the time axis. As is also easily understood from thisgraph, the error tolerance can be improved by aggregating high-priorityMPDUs at forward positions on the time axis.

Third Embodiment

The third embodiment of the present invention is directed to theexecution of sliding window control for frame aggregation in QoS basedon the HCCA scheme. A communication apparatus according to the thirdembodiment applies sliding window control to MAC frames delimited in onePHY frame according to the respective priorities.

In this case, sliding window control is a technique for properlycontrolling retransmission addressed to the same terminal inconsideration of the fairness and QoS (Quality of Service) ofcommunication. A sliding window used for this control is expressed by atransmission management table representing transmission and receptionhistories including a retransmission history.

Consider a situation wherein a given transmitting communicationapparatus consecutively transmits MAC frames (MPDUs) to the samereceiving communication apparatus preferentially over othercommunication apparatuses. In order to prevent transmission andreception rights from being disproportionately assigned to a specificcommunication apparatus, the number of MAC frames that can beconsecutively transmitted is limited on the basis of the transmissionmanagement table. Assume that this limitation is effective until eitherthe transmitting communication apparatus or the receiving communicationapparatus is changed. According to sliding window control, the overflowof the buffer in a receiving terminal due to excessive retransmission.

Conventionally, when, for example, an error occurs in the first MACframe in a MAC super frame, even if the remaining MAC frames areproperly received, they are not forwarded to an upper layer on thereceiving side, and the subsequent MAC frame is stored in the buffer (toprevent sequence reversal problem at receiving side). If thetransmitting side finds the error in the first MAC frame upon checking areturned partial Ack frame, the transmitting side retransmits only thefirst MAC frame without adding any new frame. If such a conventionalmethod is applied to a MAC super frame containing frames with differentpriorities without any change, the following problem arises.

Assume that frames having different priorities are aggregated like“high”, “high”, “intermediate”, “intermediate”, “intermediate”, “low”,“low”, and “low”, and transmitted, and the reception state isrepresented by “01111110” (note that “1” indicates a successfulreception determined by CRC check; “0”, an error).

Unique sequence numbers are respectively assigned to the MAC frames foreach TID (even if sequence numbers become redundant, the correspondingMAC frames can be uniquely identified with different TIDs). In thiscase, all frames with an intermediate priority are thought to beforwarded to an upper layer at the receiving terminal. If, however,sliding window control for frame aggregation is applied to thisoperation without any change, since the first MAC frame in the MAC superframe has an error, all the remaining MAC frames cannot be forwarded tothe upper layer.

In order to solve this problem, the third embodiment of the presentinvention executes independent sliding window control for each priority.In the above case, in the high-priority category, the first MAC framehas an error, and hence the remaining frames are buffered. In theintermediate-priority category, all the frames are properly received andhence can be forwarded to the upper layer. In the low-priority category,after the first MAC frame is transferred to the upper layer, theretransmission of the next MAC frame is waited for. As in the firstembodiment, if a MAC super frame having two Ack Policies, i.e., “No_ACK”and “Partial_ACK”, is received, all data frames corresponding to theNo_ACK policy may be unconditionally forwarded to the upper layer.

The transmitting terminal determines on the basis of the lifetime ofeach MAC frame whether to retransmit or discard the frame. If the windowsize of a sliding window is unlimited, the frame length of a MAC superframe becomes unnecessarily large. For this reason, the maximum windowsize for each TS is preferably determined in advance using informationof a TSPEC (e.g. Mean Data Rate, Delay Bound).

Retransmission control for each priority will be described in detailbelow. First of all, unlike in the IEEE 802.11 legacy standard, in theIEEE 802.11e standard, sequence numbers are independently assigned forthe respective TIDs (TSIDs in the case of HCCA). For example,consecutive sequence numbers exist in the respective TSIDs like “0 1 2 34 5, . . . ” in TSID for VoIP, “0 1 2 3 4 5, . . . ” in TSID for Video,and “0 1 2 3 4 5, . . . ” in TSID for FTP. On the QoS data receivingside, if frames are consecutive for each TSID, the frames can bereleased from the reception buffer and transferred to the upper layer.

FIG. 23 is a view showing an example of retransmission control for eachpriority. When MPDUs with different priorities are to be aggregated intoa MAC super frame, the transmitting terminal stores in advance therelative positional relationship of the respective priorities in the MACsuper frame. This information is required when the terminal performssliding window control for each priority upon reception of a PartialAck. Note that the window size of a sliding window is determined foreach priority and can be variable in length.

Referring to FIG. 23, reference numeral 170 denotes a frame sequencewith a high-priority TSID for VoIP; 171, a frame sequence with anintermediate TSID for Video; and 172, a frame sequence with alow-priority TSID for FTP. As shown in FIG. 23, sliding windows 1700,1710, and 1702 having start points are set for the respective framesequences. The frames corresponding to the respective sliding windows1700, 1710, and 1720 are aggregated to construct a MAC super frame 173in a transmitting terminal 100.

Assume that errors have occurred at “1” of a high-priority MPDU and “2”of a low-priority MPDU as a result of CRC calculation (1800), as shownin FIG. 24. Reference numeral 1801 denotes a receiving-side buffer. Atthis time, in the receiving-side buffer state corresponding to thehigh-priority MPDU portion, MPDUs “2” and “3” are set in the standbystate to wait for MPDU “1”. There are no frames corresponding to theintermediate-priority portion. In the low-priority portion, althoughMPDU “2” is actually waited for, since the MPDU with the precedingsequence number has been successfully received, no frames are present inthe buffer 1801.

On the receiving terminal 110 side, Frames which have not beenconsecutively received are left in the buffer 1801 to wait forretransmission from the transmitting side. Otherwise, frames arereleased from a reception buffer 1801 and forwarded to the upper layer.

As shown in FIG. 25, on the receiving side, as in frame aggregation, thereception statuses of the respective MPDUs in the MAC super frame arebitmapped, and a Partial Ack 190 is returned to the transmitting side.When the Partial Ack 190 is returned to the transmitting terminal 100,the transmitting terminal 100 performs sliding window control on thebasis of relative positional information 191 of the priority MPDUs whichhave been cached at the time of the transmission of the MAC super frame.For example, upon referring to a returned Partial Ack Bitmap 192, thetransmitting terminal shifts the start point corresponding to eachpriority, as shown in FIG. 25. When a MAC super frame is to beretransmitted, new frames are aggregated in accordance with therespective start points to construct a MAC super frame 174 to beretransmitted.

As described above, although the maximum window size is determined foreach priority, frames with high priorities are preferentially packedinto a MAC super frame. When the number of frames aggregated reaches themaximum count (the count depends on the receiver buffer size, and isdetermined transmitting and receiving side) determined by one PHY frame,if there is no space in which MAC frames with low priorities can bepacked, the aggregation of frames into a MAC super frame is immediatelyabandoned (frames with high priorities are aggregated preferentiallyover frames with low priorities).

Fourth Embodiment

The fourth embodiment of the present invention is directed to acommunication apparatus which transmits many Block Ack control frames(Block Ack Request/Block Ack for each priority) defined in IEEE 802.11eupon containing them in one PHY frame. IEEE 802.11e defines a Block Ackby which data frames are transmitted at SIFS intervals in a burstmanner. A communication sequence based on Block Ack can be executed evenif the frame aggregation described above is not performed.

FIG. 26 is a view showing an example of a Block Ack sequence. Accordingto a normal sequence, after QoS data 260 is transmitted in a burstmanner, a Block Ack Request 261 is sent for each priority, and a BlockAck 262 indicating a reception status is received from the receivingterminal. That is, the Block Ack Request 261 and Block Ack 262 arerepeatedly transmitted and received by the number of times correspondingto the number of priorities (e.g. TSs in HCCA protocol).

In contrast to this, in the fourth embodiment, a reduction in excessiveoverhead is achieved by aggregating Block Ack Requests (or Block Acks)for the respective priorities into one PHY frame.

According to IEEE802.11e standard, a Block Ack Request frame containsBAR control field and Block Ack Starting Sequence Control in addition tothe MAC Header. In the BAR Control field, a TID for identifying apriority and a reserved bit are present. The Block Ack Starting SequenceControl field indicates the sequence number of the first MAC frame inthe bursty transmission corresponding to priority. That is, the BARControl and Block Ack Starting Sequence Control fields are informationrequired for each priority.

The frame format of a Block Ack is similar to that of a Block AckRequest but differs in that the Block Ack has a Block Ack Bitmap fieldcontaining the bitmap of reception statuses on the receiving terminalside (each status indicating upon CRC calculation for each MAC framewhether or not the frame is successfully received). The informationrequired for each priority includes BAR control, Block Ack StartingSequence Control, and Block Ack Bitmap fields.

As shown in FIG. 27, in this embodiment wherein Block Ack Requests forthe respective priorities are aggregated into one PHY frame, anaggregation frame 270 has the following format with a MAC header beinglocated at its head. That is, this format is designed as [MACHeader]—[“BAR Control 1”, “Block Ack Starting Sequence Control 1”] [“BARControl 2”], [“Block Ack Starting Sequence Control 2”] [“BAR Control 3”,“Block Ack Starting Sequence Control 3”] . . . —[FCS]. In the aboveframe format, the MAC header and FCS are attached to the Block AckRequest information for each TS.

When Block Acks for the respective priorities are aggregated into onePHY frame, BAR Control, Block Ack Starting Sequence Control, and BlockAck Bitmap fields are prepared for each priority, with one MAC Headerand one FCS being attached. As shown in FIG. 28, an aggregation frame271 is designed as [MAC Header]—[“BAR Control 1”, “Block Ack StartingSequence Control 1”, Block Ack Bitmap 1] [“BAR Control 2”, “Block AckStarting Sequence Control 2”, Block Ack Bitmap 2] [“BAR Control 3”,“Block Ack Starting Sequence Control 3”, Block Ack Bitmap_(—)3] . . .-[FCS].

After Block Ack Requests (or Block Acks) are aggregated into one PHYframe in the above manner, Block Ack Starting Sequence Control isperformed as in normal IEEE 802.11e. When immediate Block Ack protocolis to be used, the transmitting terminal outputs an aggregated Block AckRequest first, and then waits for the reception of an aggregated BlockAck. Upon receiving the aggregated Block Ack, Block Ack Request thetransmitting terminal retransmits QoS data frames in accordance with therespective Block Ack Bitmaps. Assume that Block Ack protocol is to beused. In this case, after an aggregated Block Ack Request istransmitted, the receiving terminal transmits a Normal Ack frame for theBlock Ack Request, and transmits an aggregated Block Acks after certainperiod of time. The transmitting terminal transmits an a Normal Ackframe corresponding to the Block Ack frame received from the receivingside, and begins a retransmission process.

FIG. 29 shows an example of the frame sequence of a immediate Block Ack.The immediate Block Ack is a sequence in which after the transmittingside transmits a Block Ack Request, the receiving side immediatelyreturns a response (Block Ack). In this sequence, Block Ack Request andBlock Ack for each plurality of priorities (strictly speaking TIDs) arecombined, and an aggregate Block Ack Request 290 and an aggregated BlockAck 291 are used. Referring to FIG. 29, TXOP signifies the interval oftime when a particular terminal has the right to frame exchangesequences onto the wireless medium. Also, QoS CF-Poll (ContentionFree-Poll) means a QoS compatible polling frame transmitted by the HC109 to permit a QSTA 100 to perform transmission. At the time ofdownlink transmission from the HC 109, no QoS CF-Poll frame is required.

The delayed Block Ack sequence shown in FIG. 30 is a delayed typesequence in which when the transmitting side transmits a Block AckRequest, the receiving side returns a response (Block Ack) after awhile. In the delayed Block Ack sequence, a Normal Ack frame 601 isrequired for each of Block Ack Request and Block Ack. As shown in FIG.30, in the delayed Block Ack sequence, an aggregate Block Ack Request600 and aggregate Block Ack 602 are used.

According to the fourth embodiment, there can be provided acommunication apparatus which transmits Block Ack Request or responsemessages defined for the respective TIDs by using one PHY frame(aggregates Block Ack messages).

The above embodiments of the present invention described above canprovide functions and effects such as being capable of guaranteeing thequality of an application sensitive to delays and, for example, keepingjitter uniform and realizing more efficient transfer (guaranteeing evena bandwidth for low-priority flows) by aggregating a plurality of flowscorresponding to one destination. In addition, assigning weights for therespective destination STAs (users) makes it possible to easily realizeservice quality classification based on an accounting system. This makesit possible to cause an AP to transmit a frame preferentially, by WRR,to the terminal of a user who pays a high fee.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

1. A communication apparatus comprising: a frame generating deviceconfigured to generate a physical frame containing, of a plurality ofMAC frames to be transmitted, a MAC frame which requires acknowledgementindicating that the frame is received by a receiving side, a MAC framewhich does not require the acknowledgement, and identificationinformation which indicates necessity/unnecessity of acknowledgement forsaid each MAC frame depending on whether said each MAC frame requiresacknowledgement; and a transmitting device configured to transmit thephysical frame generated by the frame generating device.
 2. An apparatusaccording to claim 1, further comprising a setting device configured toset a control information in accordance with PCF or HCF control access.3. An apparatus according to claim 2, wherein the identificationinformation is set depending on whether the MAC frame contained in aheader portion of the MAC frame conforms to communication based onpriority of the PCF or HCF control access.
 4. An apparatus according toclaim 1, further comprising: a first storage device configured to storea MAC frame requiring the acknowledgement and information about theframe; and a second storage device configured to store at leastinformation about a MAC frame which does not require theacknowledgement.
 5. An apparatus according to claim 4, furthercomprising: a receiving device configured to receive an acknowledgementresponse for a MAC frame contained in the physical frame; and aretransmitting device configured to retransmit a MAC frame requiringretransmission on the basis of the acknowledgement response andinformation stored in the storage device.
 6. A communication apparatuscomprising: a receiving device configured to receive a physical framecontaining a plurality of MAC frames and identification information, forsaid each MAC frame, which indicates whether or not an acknowledgementresponse indicating that the MAC frame is received is required; aresponse generating device configured to generate an acknowledgementresponse indicating whether or not each of a plurality of MAC framescontained in the physical frame could be received, on the basis of areception result obtained from the receiving device for each of MACframes contained in the physical frame and information about the MACframe which is indicated by the identification information; and aresponse transmitting device configured to transmit an acknowledgementresponse generated by the response generating device.
 7. An apparatusaccording to claim 6, which further comprises an error detection deviceconfigured to detect a reception error indicating that reception of anyone of MAC frames contained in the physical frame has failed, and inwhich the response generating device determines, on the basis of theidentification information, whether or not necessity of acknowledgementis designated for a MAC frame in which a reception error has beendetected, and if necessity of an acknowledgement response is designated,designates, as the acknowledgement response, information indicating thatthe MAC frame in which the reception error has been detected has notbeen able to be received.
 8. A communication method comprising: a framegenerating step of generating a physical frame containing, of aplurality of MAC frames to be transmitted, a MAC frame which requiresacknowledgement indicating that the frame is received by a receivingside, a MAC frame which does not require the acknowledgement, andidentification information which indicates necessity/unnecessity ofacknowledgement for said each MAC frame depending on whether said eachMAC frame requires acknowledgement; and a transmitting step oftransmitting the physical frame generated in the frame generating step.9. A method according to claim 8, further comprising a setting step ofsetting a control information in accordance with PCF or HCF controlaccess.
 10. A method according to claim 9, wherein the identificationinformation is set depending on whether the MAC frame contained in aheader portion of the MAC frame conforms to communication based onpriority of the PCF or HCF control access.
 11. A method according toclaim 8, further comprising: a first storage step of storing a MAC framerequiring the acknowledgement and information about the frame; and asecond storage step of storing at least information about a MAC framewhich does not require the acknowledgement.
 12. A method according toclaim 11, further comprising: a receiving step of receiving anacknowledgement response for a MAC frame contained in the physicalframe; and a retransmitting step of retransmitting a MAC frame requiringretransmission on the basis of the acknowledgement response andinformation stored in the storage device.
 13. A communication methodcomprising: a receiving step of receiving a physical frame containing aplurality of MAC frames and identification information, for said eachMAC frame, which indicates whether or not an acknowledgement responseindicating that the MAC frame is received is required; a responsegenerating step of generating an acknowledgement response indicatingwhether or not each of a plurality of MAC frames contained in thephysical frame could be received, on the basis of a reception resultobtained in the receiving step for each of MAC frames contained in thephysical frame and information about the MAC frame which is indicated bythe identification information; and a response transmitting step oftransmitting an acknowledgement response generated in the responsegenerating step.
 14. A method according to claim 13, which furthercomprises an error detection step of detecting a reception errorindicating that reception of any one of MAC frames contained in thephysical frame has failed, and in which in the response generating step,it is determined, on the basis of the identification information,whether or not necessity of acknowledgement is designated for a MACframe in which a reception error has been detected, and if necessity ofan acknowledgement response is designated, information indicating thatthe MAC frame in which the reception error has been detected has notbeen able to be received is designated as the acknowledgement response.15. A communication system comprising: a transmitting terminal includinga frame generating device configured to generate a physical framecontaining, of a plurality of MAC frames to be transmitted, a MAC framewhich requires acknowledgement indicating that the frame is received bya receiving side, a MAC frame which does not require theacknowledgement, and identification information which indicatesnecessity/unnecessity of acknowledgement for said each MAC framedepending on whether said each MAC frame requires acknowledgement, and atransmitting device configured to transmit the physical frame generatedby the frame generating device; and a receiving terminal including areceiving device configured to receive a physical frame containing aplurality of MAC frames and identification information, for said eachMAC frame, which indicates whether or not an acknowledgement responseindicating that the MAC frame is received is required, a responsegenerating device configured to generate an acknowledgement responseindicating whether or not each of a plurality of MAC frames contained inthe physical frame could be received, on the basis of a reception resultobtained from the receiving device for each of MAC frames contained inthe physical frame and information about the MAC frame which isindicated by the identification information, and a response transmittingdevice configured to transmit an acknowledgement response generated bythe response generating device.
 16. A communication apparatus comprisinga transmitting device configured to transmit a physical frame having aMAC super frame payload which is divided into a first block for storingat least one first MAC frame having a first priority and a second blockfor storing at least one second MAC frame having a second priority. 17.An apparatus according to claim 16, wherein the first block and thesecond block are arranged in the MAC super frame payload such that thefirst block follows a MAC super frame header, and the second blockfollows the first block.
 18. An apparatus according to claim 16, whereinthe first priority corresponds to a first traffic identifier of thefirst MAC frame, and the second priority corresponds to a second trafficidentifier of the second MAC frame.
 19. An apparatus according to claim18, wherein the first traffic identifier and the second trafficidentifier correspond to a first traffic stream and a second trafficstream set on the basis of a first traffic specification and a secondtraffic specification.
 20. An apparatus according to claim 16, whereinthe first block corresponds to a first transmission channel stateestimated by channel estimation, and the second block corresponds to asecond transmission channel state estimated by channel estimation.
 21. Acommunication apparatus comprising a receiving device configured toreceive a physical frame transmitted from a communication apparatusdefined in claim
 16. 22. A communication apparatus comprising: atransmitting device configured to transmit a physical frame having a MACsuper frame payload which is divided into a first block for storing atleast one first MAC frame having a first priority and a second block forstoring at least one second MAC frame having a second priority; areceiving device configured to receive a partial response frame for thephysical frame; a retransmitting device configured to retransmit any oneof MAC frames contained in the MAC super frame payload in accordancewith the partial response frame; and a retransmission control deviceconfigured to control retransmission by the retransmitting device inaccordance with a first window size corresponding to the first priority,and control retransmission by the retransmitting device in accordancewith a second window size corresponding to the second priority.
 23. Anapparatus according to claim 22, wherein an upper limit of the number ofretransmissions by the retransmitting device is determined on the basisof delay bound information.
 24. An apparatus according to claim 22,wherein the first window size and the second window size are determinedon the basis of a first mean data rate and a second mean data raterespectively representing a first traffic specification and a secondtraffic specification.
 25. A communication method comprising: atransmitting step of transmitting a physical frame having a MAC superframe payload which is divided into a first block for storing at leastone first MAC frame having a first priority and a second block forstoring at least one second MAC frame having a second priority; areceiving step of receiving a partial response frame for the physicalframe; a retransmitting step of retransmitting any one of MAC framescontained in the MAC super frame payload in accordance with the partialresponse frame; and a retransmission control step of controllingretransmission in the retransmitting step in accordance with a firstwindow size corresponding to the first priority, and controllingretransmission in the retransmitting step in accordance with a secondwindow size corresponding to the second priority.
 26. A method accordingto claim 25, wherein an upper limit of the number of retransmissions inthe retransmitting step is determined on the basis of delay boundinformation.
 27. A method according to claim 25, wherein the firstwindow size and the second window size are determined on the basis of afirst mean data rate and a second mean data rate respectivelyrepresenting a first traffic specification and a second trafficspecification.
 28. A communication apparatus comprising: a datatransmitting device configured to transmit a series of QoS datacorresponding to a plurality of traffic identifiers; and a control frametransmitting device configured to transmit a single control framecontaining a plurality of Block Ack Requests corresponding to saidplurality of traffic identifiers.
 29. An apparatus according to claim28, wherein a immediate response sequence of receiving a Block Ack forthe Block Ack Request within a polled TXOP period is executed.
 30. Anapparatus according to claim 29, wherein a delayed response sequence ofreceiving a Block Ack for the Block Ack Request a predetermined periodof time after a polled TXOP period.
 31. A communication apparatuscomprising: a data receiving device configured to receive a series ofQoS data corresponding to a plurality of traffic identifiers; a controlframe receiving device configured to receive a single control framecontaining a plurality of Block Ack Requests corresponding to saidplurality of traffic identifiers; and a response transmitting deviceconfigured to transmit a single response frame containing a plurality ofBlock Acks corresponding to said plurality of Block Ack Requests inresponse to the control frame.
 32. An apparatus according to claim 31,wherein a immediate response sequence of transmitting the response framewithin a polled TXOP period is executed.
 33. An apparatus according toclaim 32, wherein a delayed response sequence of receiving the responseframe a predetermined period of time after a polled TXOP period isexecuted.
 34. A communication method comprising: a data transmittingstep of transmitting a series of QoS data corresponding to a pluralityof traffic identifiers; and a control frame transmitting step oftransmitting a single control frame containing a plurality of Block AckRequests corresponding to said plurality of traffic identifiers.
 35. Amethod according to claim 34, wherein a immediate response sequence ofreceiving a Block Ack for the Block Ack Requests within a polled TXOPperiod is executed.
 36. A method according to claim 34, wherein adelayed response sequence of receiving a Block Ack for the Block AckRequest a predetermined period of time after a polled TXOP period isexecuted.
 37. A communication method comprising: a data receiving stepof receiving a series of QoS data corresponding to a plurality oftraffic identifiers; a control frame receiving step of receiving asingle control frame containing a plurality of Block Ack Requestscorresponding to said plurality of traffic identifiers; and a responsereceiving step of receiving a single response frame containing aplurality of Block Acks corresponding to said plurality of Block AckRequests in response to the control frame.
 38. A method according toclaim 37, wherein a immediate response sequence of transmitting theresponse frame within a polled TXOP period is executed.
 39. A methodaccording to claim 37, wherein a delayed response sequence of receivingthe response frame a predetermined period of time after a polled TXOPperiod.
 40. A communication system comprising: a first communicationapparatus including a data transmitting device configured to transmit aseries of QoS data corresponding to a plurality of traffic identifiers,and a control frame transmitting device configured to transmit a singlecontrol frame containing a plurality of Block Ack Requests correspondingto said plurality of traffic identifiers; and a second communicationapparatus including a data receiving device configured to receive aseries of QoS data corresponding to a plurality of traffic identifiers,a control frame receiving device configured to receive a single controlframe containing a plurality of Block Ack Requests corresponding to saidplurality of traffic identifiers, and a response transmitting deviceconfigured to transmit, to the first communication apparatus, a singleresponse frame containing a plurality of Block Acks corresponding tosaid plurality of Block Ack Requests in response to the control frame.